Lotus Elan

Elan S4/Sprint Wiring Diagram.....

PostPost by: Phil.C60 » Sat Apr 23, 2022 7:29 am

Hello All, I'm sure this subject has been discussed before, but please bear with me, I'm new here!
I have just acquired an Elan S4 which is/was apparently a Sprint. It 's chassis plate indicates 7105, ie May 1971, G suffix, Type No. 45 which is correct (it's a convertible), engine code N.
The car is in reasonable overall condition, but unsurprisingly has had various bits fiddled with over the years especially the headlamp wiring. There is no sign of the "Flash" relay, the headlamp pin switches are missing, and the main and dip relays have permanent grounds. The headlamps work, albeit even when they are down.
This car appears to have been fitted with an alternator from new: there is no sign of a control box having been removed (unless someone has done a super-duper wiring job....which is not apparent). I cannot find anywhere a wiring diagram for an S4 with an alternator. I have a copy of the March 1970 genuine workshop manual which suggests that an alternator may be fitted, but only contains wiring diagrams for dynamo/control box versions. Does the correct diagram exist? Does anyone have one? I could work it all out if I have to, but it would be much easier with a diagram! Thanks in advance, Phil
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PostPost by: jcocking » Sat Apr 23, 2022 9:05 am

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PostPost by: billwill » Sat Apr 23, 2022 12:20 pm

Technically, I believe that that FLASH facility is deemed illegal, so many of those who reworked their wiring removed the automatic flash facility.
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PostPost by: Andy8421 » Sun Apr 24, 2022 6:31 am

I removed the headlamp 'microswitches' (as I believe have many others) primarily because they were unreliable rubbish. Originally designed as courtesy light switches (and they weren't much good at that), they were designed so the moving contact and spring were shielded in the door pillar and connected to earth via the mounting screws.

In the Elan, they are exposed to the elements and fail. Unless you think you will accidentally switch the headlights on with the lights retracted, I wouldn't bother replacing them.
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PostPost by: Phil.C60 » Sun Apr 24, 2022 6:58 am

The reason for my question about the correct diagram is this: In the original diagram, for a dynamo car, the blue cable which is the feed to the headlamp relays appears to come from a junction at the control box with a brown cable from the solenoid which is permanently live (and also feeds terminal 1 on the ignition switch via the brown/blue cable and brown cable at the bulkhead). This is fine with the pin switches fitted, because the relays are only grounded with the headlamps up. If you then delete the pin switches and ground the relays permanently, they are energised all the time and you have an instant current drain of approximately (in my experience) 0.3A which will flatten your battery over a weekend. Hence my question about the correct diagram for my car: as the control box is not present, where does the blue wire come from.....if it comes from the lighting switch, that's fine because it's only live with the lights on. If it comes from a harness junction with a brown cable it isn't, because it's live all the time. Yes, the car does have a battery master switch so in reality it probably doesn't matter as long as you always turn it off, and yes I can check all this and work it out, but I just thought I'd ask the question because I can't be the first person to think about this! And I would really like to have the correct wiring diagram for the car. It's much easier to work out how to modify something if you know how it works in the first place......
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PostPost by: elanner » Sun Apr 24, 2022 11:00 am

Uh, that doesn't sound quite right. If the pin/micro switches are removed then one of relays will turn on, but only when the dashboard light switch is on. Which relay turns on will depend on the position of the dip/main steering column arm. Think of Elans with failsafe headlamps that raise by themselves as the vacuum decays when the car is parked - they don't all end up with flat batteries.

The blue 12V from the bulkhead control box is for the high current, load side of the relay. The pin/micro switch is for the low current, control side of the relay.

Regarding unreliable pin/micro switches I hedged my bets by strapping a link across the switched side of them - BR to BP. Then, if either one fails the other will do the trick. (It's easy enough to check the two switches individually every once in while by lifting each headlamp pod manually when the lights are switched on.)

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PostPost by: Craven » Sun Apr 24, 2022 11:23 am

Never been able to find a diagram for an alternator, but all Elans I think follow the same arrangement.
Blue feed is always Hot, lights controlled by the Dash Switch, this controls the 2 relays coil feeds via the head/dip switch UB & UN on the + side, the ground side of relays go to chassis via the micro switches.
So relay wire BR taken straight to ground changes nothing. Only if you leave the head lights ON with Dash Switch you leave the head lights ON.
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PostPost by: Phil.C60 » Sun Apr 24, 2022 5:33 pm

Oops! Just realised the error of my ways. The diagram is not clear with regard to the relay terminals, and I now see that the blue is the feed for the lamps on terminal 30 and the relay windings are controlled by the main/dip switch. Silly me.
I'd still like a proper diagram though. :D
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PostPost by: Bodmin » Sun Apr 24, 2022 9:52 pm

Download from this thread.

viewtopic.php?f=38&t=36033&start=
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PostPost by: Bodmin » Sun Apr 24, 2022 9:53 pm

71 Elan Sprint FHC Pistachio
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PostPost by: Andy8421 » Mon Apr 25, 2022 5:56 am

Phil.C60 wrote:I'd still like a proper diagram though. :D

I have never seen a wiring diagram with an alternator either. It would be good to have it posted on here if you come across one.

My manual is the March '70 version - I am not sure if a later version exists. The Elan was coming to the end of its life when the Sprint came along and I wonder if they just gave up keeping the manual up to date (though there is a whole section on how to test the alternator in the manual - which is odd since the wiring diagram doesn't show it).

By now, many Elans will have had their wiring loom replaced, so it is possible that you have an after market loom that was made to accommodate an alternator. My Sprint is '7110XXX', so built after yours and was supplied with a dynamo. Are there 4 tell-tale holes on the bulkhead where the control box would have fitted?
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PostPost by: Phil.C60 » Mon Apr 25, 2022 6:40 am

I can't see any holes, no. And usually, when an alternator is retro-fitted to a dynamo car the control box is left in place as a bus bar and to connect the warning light circuit. Unless as I said it's had a super-duper wiring harness re-configuration (which is not evident) or a re-wire/new harness, which is always a possibility (it is 50 years old after all....). With regards to your car having a dynamo, as both things are shown in the 1970 manual, was it an optional item perhaps?
My car is a bit odd: was originally red-over-white (now yellow), spent some time in Sweden where it was registered as a Sprint, and has an "N" engine code. However, it has a bulge in the bonnet, side entry front callipers and an ignition switch in the dash. Who knows. Tim Wilkes certainly thinks it's and early Sprint. I got the car for a very good price, it needs some recommissioning (rotoflexes, front brakes, clutch hydraulics, starter motor, battery etc.) but is essentially sound (galvanised chassis with correct "LR" number and square cross member/ vacuum tank, rear callipers are OK, body is not bad) and apparently has some competition history in Sweden (has fixed plastic side windows and a proper substantial roll bar that has side members along the inside of the sills with returns in the footwells to the front of the chassis). I'm dancing as fast as I can to try and get it roadworthy for the summer and move forwards from there....
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PostPost by: Andy8421 » Mon Apr 25, 2022 7:41 am

Phil,

I believe it is generally accepted that the Sprints started at 7101XXXX, so yours would be well into the Sprint era. The challenge for purists is that Lotus seems to have fitted whatever was available as the car came down the line - this was particularly the case close to model change dates. I have seen reports that the bonnet bulge was fitted to some Sprints.

According to Robinshaw/Ross, the top entry calipers were introduced in September '71 - mine has them, but it would be consistent if yours didn't. The ignition steering lock apparently was introduced in 1972, but mine also has one. Interestingly Robinshaw/Ross don't list an alternator as original equipment. Robinshaw/Ross could of course be wrong on any of these points.

It depends how precious you want to be about things. Lotus weren't great at keeping records, and apparently a number of records were destroyed, so who is to say what was and wasn't fitted to your car. In the US they are particularly keen on 'matching numbers', a Lotus Elan doesn't really lend itself to that approach....
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PostPost by: Phil.C60 » Mon Apr 25, 2022 8:08 am

Thanks for that information Andy, that makes sense to me. Car also has red cam cover rather than "Big Valve"
(although I know a man very near me who has a spare....) which again was apparently often the case. I am by no means a purist, the car will be what it will be, I am not averse to modern improvements when they offer an advantage: Alternators are better than dynamos, modern radiators are for more efficient, as are proper electric fans with shrouds - mine has the open original fan that probably slings air everywhere except where you'd like it! The only thing I will do is only make "reversible" mods and keep the original parts. It's going to be a voyage of discovery, but hopefully with a pleasant outcome! There are some ugly but sound fibreglass repairs where you can't see them (drivers floor pan etc.) and some minor gel coat cracks and chips which will get some attention in the future, but for now it's just time to make it "good enough" and use it.
Thanks again for taking the time to reply Andy.
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PostPost by: Craven » Mon Apr 25, 2022 10:50 am

I’ve looked for late +2 circuit diagrams for an alternator but still unable to find a factory version.
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